What is a MetaAnalysis Metaanalysis is the statistical

What is a Meta-Analysis? Meta-analysis is the statistical procedure for combining data from multiple studies. Ø Meta-analysis refers to the analysis of analyses Ø When the treatment effect (or effect size such as: correlation coefficients, oddsratios, proportions) is consistent from one study to the next, meta-analysis can be used to identify this common effect. Ø When the effect varies from one study to the next, meta-analysis may be used to identify Ø

Why do a Meta-Analysis? Decisions about the utility of an intervention or the validity of a hypothesis cannot be based on the results of a single study, because results typically vary from one study to the next. Ø Rather, a mechanism is needed to synthesize data across studies. Ø Narrative reviews had been used for this purpose, but the narrative review is largely subjective (different experts can come to different conclusions) Ø

and becomes impossibly difficult when there are more than a few studies involved. Ø Meta-analysis, by contrast, applies objective formulas (much as one would apply statistics to data within a single study), and can be used with any number of studies. Ø

Meta-Analysis are important in applied and basic research Pharmaceutical companies use metaanalysis to gain approval for new drugs, with regulatory agencies sometimes requiring a meta-analysis as part of the approval process. Ø Clinicians and applied researchers in medicine, education, psychology, criminal justice, and other fields use meta-analysis to determine which interventions work, and which ones work best. Ø

Meta analysis is also widely used in basic research to evaluate the evidence in areas as diverse as Ø sociology, Ø social psychology, Ø sex differences, Ø finance and economics, Ø political science, Ø marketing, Ø ecology and genetics, Ø among others. Ø

Where does Meta-Analysis fit in the research process? Publications Ø Planning new studies Ø Grant applications Ø

Publications Many journals encourage researchers to submit systematic reviews and metaanalyses that summarize the body of evidence on a specific question, and this approach is replacing the traditional narrative review. Ø Meta-analyses also play supporting roles in other papers. Ø For example, a paper that reports results for a new primary study might include a meta-analysis in the introduction to synthesize prior data and help to place the Ø

Planning new studies Meta-analyses can play a key role in planning new studies. Ø The meta-analysis can help identify Ø which questions have already been answered and which remain to be answered, Ø which outcome measures or populations are most likely to yield significant results, and which variants of the planned intervention are likely to be most powerful. Ø

Grant applications Meta-analyses are used in grant applications to justify the need for a new study. Ø The meta-analysis serves to put the available data in context and to show the potential utility of the planned study. Ø The graphical elements of the meta-analysis, such as the forest plot, provide a mechanism for presenting the data clearly, and for capturing the attention of the reviewers. Ø Some funding agencies now require a metaØ

Aims ﻣﺘﺎآﻨﺎﻟﻴﺰ ﺍﺯ ﻫﺪﻑ 1. 2. 3. 4. 5. 6. 7. Increases the statistical power of a comparison Improves the estimation of the effect of a treatment Combines the results of studies that are contrasting Answers new questions Analysis sub-groups of subjects selected from different studies Analysis trends (e. g within a time- frame…) Defines areas in which further studies are

tance of meta-analysis in evidence-based medicine(EBM) Meta-analysis RCT Before-after clinical trials Cohort Studies Case-control Studies Cross-sectional Studies Case series Studies Case Report Studies

Which Studies to Include? It is critical to have an explicit inclusion and exclusion criteria The broader the research domain, the more detailed they tend to become Refine criteria as you interact with the literature

Components of a detailed criteria distinguishing features research respondents key variables research methods cultural and linguistic range time frame publication types

When Can You Do Metaanalysis? Meta-analysis is applicable to collections of research that: Are empirical, rather than theoretical Produce quantitative results, rather than qualitative findings Examine the same constructs and relationships Have findings that can be configured in a comparable statistical form (e. g. , as effect sizes, correlation coefficients, odds-ratios, proportions)

Searching Far and Wide Potential sources for identification of documents Computerized bibliographic databases “Google” internet search engine Authors working in the research domain (email a relevant Listserv? )

Conference programs Dissertations Review articles Hand searching relevant journal Government reports, bibliographies, clearinghouses

Timely response A classic example: streptokinase in myocardial infarction First trial published in 1959 15 trials published up to 1977 Introduced as normal practice in late 80 s Meta-analysis of treatments in 1992: fall in mortality by 1977, after inclusion of 15 trials

Thrombolytic Therapy Textbook/Review Recommendations 2. 0 1960 2 65 1970 3 149 21 4 316 5 7 1793 10 2544 11 2651 15 3311 17 3929 22 5452 1980 1985 1990 Specific Routine 1 23 Experimental Pts Not Mentioned 1. 0 Rare/Never Cumulative Year RCTs 0. 5 P<. 01 1 10 1 2 2 8 7 23 5767 8 1 27 6125 30 6346 33 6571 43 21 059 54 22 051 65 47 185 67 47 531 70 48 154 P<. 001 P<. 00001 M M M Odds Ratio (Log Scale) Favours Treatment Favours Control 12 1 8 4 7 3 5 1 2 2 1 15 8 6 1 1

Television viewing and risk of type 2 diabetes, cardiovascular disease, and all-cause mortality: a meta- analysis. JAMA JUN 2011 CONCLUSION: Prolonged TV viewing was associated with increased risk of type 2 diabetes, cardiovascular disease, and all-cause mortality

Risk of incident diabetes with intensiv -dose compared with moderate-dose statin therapy: a metaanalysis. JAMA 2011 CONCLUSION: In a pooled analysis of data from 5 statin trials, intensive-dose statin therapy was associated with an increased risk of new-onset diabetes compared with moderate-dose statin therapy.

Prevalence and trend of hepatitis C virus infection among blood donors in Iran: A systematic review and meta‑analysis Mazaher Khodabandehloo, Daem Roshani, Kourosh Sayehmiri

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